Engine



Feb. 7, 1961 R. w. HULL 2,970,582

ENGINE AFiled. Dec. 16, 195'? 57 WMM 2775` United States atent ENGINERoy W. Hull, Painesville, Ohio, assignor to Thompson Ramo WooldridgeInc., a corporation of Ohio Filed Dec. 16, 1957, Ser. No. 703,171

8 Claims. (Cl. 12S-69) This invention relates -to an inexpensive gaseousfuel burning internal combustion engine, and more particularly relatesto a small inexpensive but eicient gas burning two-cycle internalcombustion engine having an improved fuel injection system whichintroduces the gaseous fuel after the engine ports are closed andeliminates loss of fuel with the exhaust as normally occurs in two-cycleengines.` The engines of this invention preferably have a pressurelubricating system controlled by engine crankcase pressure.

With the increasing availability of gaseous type fuels, such propane,together with the increasing acceptance and use of the fuel injectionprinciple of fuel feeding for automotive engines, there is now a needfor low-cost efficient operating gas burning internal combustion enginesusing a simplified fuel injection system and regulating device forfeeding the gaseous fuel to the engine in such a manner that the burnedfuel will not be lost with the exhaust gases.

This invention now provides small engines, fed from capsules or bottlesof propane or other gas-type fuel. The small engines of this inventionare light in weight, low in cost, easy to start and are especiallyuseful for lawnmowers, portable tools and the like.

Conventional two-cycle engines receive fuel during the exhaust strokeand lose much unburned fuel. Such engines cannot run for reasonablelengths of time on small bottles or tanks of gaseous fuel. They are thusunlit for lawnmower or power tool power plants. On the other hand, thetwo-cycle engines of the present invention have the exhaust scavengedtherefrom and the new air supply introduced and even compressed beforethe fuel is introduced.` Therefore, no unburned fuel is lost, andefficiencies comparable with heavier, more expensive fourcycle typeengines are obtained.

The two-cycle engines of this invention utilize a ported cylinder andpressurized crankcase for supplying an aircharge to the combustionchamber and for removing exhausted combustion products therefrom. Theignition system for the engine may be either in the form of a sparkplug, a glow plug, or a compression-ignition diesel type cycle. Theengines are equipped with a simple, easily mass-produced gaseous fuelinjection device which introduces the gas fuel into the enginecombustion chamber after the engine ports are closed and supplies thecorrect fuel-air ratio to the engine throughout normal changes inbarometric pressure and air density to thereby develop maximum engineefficiency and power and to prevent engine overspeed.

The fuel injection devices of the engines of this invention generallyinclude a bore in the engine block receiving a reciprocable metering rodand a check valve delining a fuel chamber therebetween. A regulatedsupply of pressurized gaseous fuel from a high-pressure reservoir orstorage source is fed to this fuel chambr before being injected into theengine. The metering rod forms an sind wall for the fuel chamber andrides on the engine Patented Fels. 7, 1961 crankshaft cam. The cam liftsthe rod to compress the fuel charge which is then injected into theengine. The check valve is backed by a spring and serves as a gatepermitting the fuel charge to liow into the combustion chamber.Injection of each fuel charge is timed to correspond with thecompression stroke of the engine through proper positioning of thecrankshaft cam lobe and the fuel volume is regulated to the desiredair-fuel ratio supplied to the combustion chamber.

It is, therefore, an object of this invention to provide a low-cost,eicient gaseous fuel burning internal combustion engine.

Another object of this invention is to provide a twocycle gaseous fuelburning internal combustion engine having an easily mass produced fuelinjection system for supplying a fuel charge to the engine combustionchamber only after the ports of the chamber are closed.

A still further object of the present invention is to provide a fuelinjection system for an internal combustion engine that is capable ofmaintaining an optimum fuel-air ratio feed to the engine while operatingthroughout normal changes in barometric pressure and air density.

A still further object of this invention is to provide a fuel injectionsystem for a gaseous fuel burning twocycle internal combustion enginethat will regulate the quantity of fuel delivered to the engine inproportion to the weight of the air charge entering the enginecombustion chamber, to thereby maintain an optimum fuel-air ratio of thecombustion mixture entering the combustion chamber.

A still further object of this invention is to provide a two-cyclegaseous fuelburning engine with a builtin fuel injection system whichdelivers optimum amounts of fuel to the combustion chamber throughoutthe normal operating range of the engine and will deliverexcessiveamounts of fuel beyond a certain designed operating enginespeed, to purposely induce a loss in eliiciency of the engine andthereby prevent development of overspeed conditions.

Other and further objects of this invention will be apparent to thoseskilled in this art from the following detailed description of theannexed sheet of drawings which forms a part of lthis specification.

In the drawings:

Figure 1. is a somewhat diagrammatic vertical crosssectional view, withparts in elevation, of a two-cycle engine according to this inventionshowing the position of the parts at the beginning of the enginecompression stroke;

Figure 2 is a View similar .to Figure l, but showing the position of theparts at the completion of the compression stroke; and

Figure 3 is a schematic view of a pressure regulator valve for theengine fuel injection device.

As shown on the drawings:

The engine assembly 10 of Figures l and 2 includes a single cylinder,two-cycle internal combustion engine E, a fuel injection assembly F, anda fuel pressure control assembly V, as better shown in Figure: 3. Thefuel injection assembly F is illustrated as integrally formed in thebody of the engine E, but it should be understood `that this assemblycould be housed. outside of the engine body, if so desired. It shouldalso be understood that the engines of this invention could be of themultiple cylinder type.

The two-cycle, single cylinder engine E, as shown, `includes a cylinderblock 11, a cylinder head l2, a crankcase 13, and a crankshaft boss 14.These portionsof the engine body can be formed in one piece or asseparate pieces.

A crankshaft is supported by the boss 14. y

The cylinder block 11 is formed with a sleeve bore 16, a fuel injectionsystem bore 17, and a crankcase chamber bore 18. The bore 18, togetherwithrthe crankcase member 13, defines a crankcase chamber 19 for theengine. This chamber 19 is subjected to air pressure as a function ofair density and engine speed, which pressure is utilized for a purposeand function that is more fully described hereinafter.

The cylinder bore 16 has a hardened, wear-resisting, cylinder sleeve 20pressed therein. An exhaust port 21 is provided through the sleeve andengine body about midway between the ends of the sleeve. An inlet port22 is provided through the sleeve at a level that partially overlaps theport 21. This port 22 is connected through a passage 22a with thecrankcase chamber 19 as shown. A third port 23 is provided through thesleeve at a level below the ports 21 and 22 to Vent the crankcasechamber 19 with the atmosphere when the piston uncovers the portas'shown in Figure 2, thereby supplying air to the crankcase chamberunderneath the piston.

A domed piston 24 is slidably mounted in the sleeve 20 and is connectedthrough a connecting rod 26 to the journal 27 of a crank pin 28 on thecrankshaft 15. The

crankshaft 15 includes a counterweight portion 29, a cam lobe 30, an oilgroove 31 and a delivery shaft portion 32. The crankshaft 15 alsoincludes an oil groove 33 that supplies lubricant from the groove 31 tothe crankpin journal 27.

The crankshaft boss 14 of the block 11 and crank- Vcase portion 13 isappropriately bored at 34 to receive shown in Figure 2, the crankcaseport 23 is uncovered and air can enter the crankcase chamber 19. Thenwhen the piston is forced downwardly on the power stroke, the port 23 isclosed and the air in the crankcase chamber 19 is compressed. As thepiston'continues its downward stroke, the exhaust -port 21 is openedandthe exhaust gases are scavenged out of the combustion chamber 40. Whilethe exhaust chamber is still opened, the inlet port 22 is uncovered bythe piston and compressed air from the crankcase 19 flows through thepassage 22a and port 22 into the combustion chamber. A portion of thisair is used to scavenge the remainder of the exhaust gases from thecombustion chamber through the port 21, and then on the succeedingupstroke of the piston,

'both ports 22 and 21 are closed so that a portion of the air from thecrankcase is trapped in the combustion chamber 40 and compressed by thepiston.

In the conventional two-cycle engine, fuel would be introduced with theair through the inlet port y22.

The engines of the present invention, however, receive fuel from thefuel injection system F when the piston is at or near the top of itsstroke.

The fuel injection system F includes a reciprocal metering rod 41, acheck valve 42, a fuel chamber 43 between "47 riding on the cam lobe 30of the crankshaft 15. A ."coil spring 48 bottomed on a counterboreshoulder 49 `in the cylinder block 11 maintains the metering rod 41against the vcam lobe 30.`

The bore 17 slidably supporting the metering rod'41 is counterbored at50 to an enlarged diameter for slidably receiving the check valve 42 andfor providing a bottoming shoulder 51 for the check valve. A coil spring52 is provided to seat the check valve 42 on the shoulder 51. Themetering passage 44 is closed by the check valve 42 when it is bottomedon the shoulder 51.

The cylinder head 12 has a bore 53 therein forming a retaining recessfor the coil spirng 52 to bottom the spring and maintain a predeterminedload thereon. A fuel pressure regulating valve assembly V shown inFigure 3 is provided to feed the correct quantity'of fuel to theinjection chamber ,43. This assembly includes a housing 54 carrying aslidable needle valve 55 with a shaft portion 56 that is connected fordifferential movement to the diaphragms of a pair of series arrangedunits 57 and S8.

rl`he valve housing 54 has a seat 59 controlled by the needle valve 55for selectively joining a conduit 60 from the gas bottle or receptacle Rwith a conduit 61 connected to the feed line 46 to the chamber 43.

Each unit 57 and 58 includes a exible diaphragm 62 dividing the unitsinto two compartments. One side of each diaphragm is vented to theatmosphere through a vent 63.' The two adjacent compartments of theunits are respectively joined through a conduit 64 with the inletpassage 46 and through -a conduit 66 with a port '67 in the crankcasechamber 19.

It will be noted that the diaphragm of unit S8 is larger than the`diaphragm of unit 57. The larger diaphragm is activated by crankcasepressure in a direction to open the needle valve 55. The smallerdiaphragm of unit 57 is actuated by pressure in the fuel line 61 and 46in a direction to close the needle lvalve. Therefore, the position ofthe needle valve will be 4determined by the relative pressures existingin the fuel supply line and the crankcase. As crankcase pressureincreases and as fuel pressure decreases the needle valve will open. Byvarying the areas of the respective diaphragms 62, the extent and ratioof movement of the needle valve 55 and the corresponding reduction orincrease in fuel volume entering the inlet passage 46 will be varied. Aproper fuel-air ratio is thereby automatically obtained.

The reservoir or gaseous fuel'bottle R can be of the replaceablecommercially available type charged with fuel at a `desired maximumpressure.

Lubrication is provided from a chamber `in the bottom of the crankcase13. As shown an extension 63 on the crankcase member 13 provides an oilsumpor chamber 69 which is closed by a bottom cap 7 t? and communicateswith the crankcase chamber 19 through a passageway 71 controlled by avalve 72 urged by spring 73 in a'direction to close they passageway 71.The oil sump is connected Vthrough the passageway 36 to the lubricationgroove 31.

Lubricantdraining tothe bottom of the crankcasef chamber 19 is returnedto the sump-69 when the pressure in the crankcase chamber is suiiicie'ntto overcome the spring load on the valve 72 thereby opening the valve.The valve will close before the crankcase chamber is\ vented to theatmosphere so that the sump will remain under pressure and provide asource of pressurized lubricant for the engine journals.

From the above description it Yshould be understood that gaseous fuelfrom the reservoir is introduced into the metering chamber 43 underthevcontrol of the needle Valve 55 which valve is regulated by crankcasepressure and gaseous fuel pressure. On the upstroke of the piston afterthe ports 21 and 22 have been closed and preferably as the piston is atvor approaches the top of its stroke, the cam lobe 311 raises themetering rod 41 to block off the passageway 46 and to compress thecharge of gas in the chamber 43 against the check valve 42. When thepressure in this chamber 43 reaches a magnitude sufficient to overcomethe spring 'loadon the check valver42,

the valve is opened and the charge of gas is forced through the passage44 into the combustion chamber above the piston. The gaseous fuel isthus injected into the combustion chamber at relatively high pressuresdepending upon the load on the check valve 42 and the 'amount of thefuel injected is controlled by a predetermined ratio of crankcasepressure and fuel pressure.

On ignition of the fuel and air mixture in the combustion chamber, thepiston 24 starts downwardly on its power stroke and closes off thecrankcase port 23 thereby increasing the pressure in the crankcasechamber 19 and tending to open the needle valve 55. The degree in whichthe valve 55 opens will depend on the pressure existing in the feed line46 and lthe extent of the pressure build up in the crankcase 19. Areduction in crankcase pressure reduces the weight of air fed to thecombustion chamber, and less fuel is then required to maintain a desiredfuel-air ratio. Preferably, the ratio of area of diaphragm 62 in unit 57to area of diaphragm 62 of unit 5S is proportioned to the ratio ofpressure in crankcase chamber 19 to fuel supply pressure in line 46.Then fuel supply pressure becomes a function of crankcase pressure. Theneedle valve 55 will close when the piston begins its upward orcompression stroke which thereby reduces the crankcase pressure.

By a choice of metering orifices the injection system can be designed toenrich the mixture as engine speed increases, thereby controllingmaximum speed of the engine without varying the setting of valve V onthe fuel bottle.

No ignition system is needed for the engine since the glow plug S isample for efficient operation.

I claim as my invention:

1. A gas engine which comprises a first cylinder, a piston slidablymounted in said first cylinder, a crankshaft driven by said piston, acam on said crankshaft, a second cylinder, a plunger slidable in saidsecond cylinder driven by said cam, means for feeding gas fuel to saidsecond cylinder, said plunger being effective to pump gas in said secondcylinder into the first cylinder, and a valve controlled by pressureunder said piston to regulate ow of gas fuel into said second cylinder.

2. In an internal combustion engine of the two-cycle type having apressurized crankcase, the improvements which com-prise a glas fuelinjection system for said engine including a source of gas fuel underpressure, a valve for metering fuel from said source, and means actuatedby pressure in the crankcase and by pressure in said source forcontrolling said valve.

3. A gas burning two-cycle engine comprising a block assembly providinga combustion chamber and a crankcase chamber, a piston slidable in theblock assembly separating the combustion and crankcase chambers, acrankshaft in the crankcase chamber driven by said piston, an air inletport for the crankcase chamber, an air inlet port for the combustionchamber receiving air from the crankcase, an exhaust port for thecombustion chamber, said piston controlling said ports to draw air intothe crankcase chamber, to force air from said crankcase chamber into thecombustion chamber and to exhaust spent gases of combustion and some airfrom the cornbustion chamber, an engine driven fuel injection deviceforcing fuel into the combustion chamber when the piston is at the topof its stroke and said combustion chamber ports are closed, and a fuelmetering valve controlled by erankcase air pressure -to regulate lfuelow to the injection device.

4. In a gaseous fuel burning internal combustion engine of the two-cycletype that includes a. piston reciprocable in a cylinder, a crankshaft, aconnecting rod connecting said piston to said crankshaft, and a closedcrankcase; a fuel injection system for admitting a charge of pressurizedfuel into said cylinder during the compression stroke of said enginecomprising, means defining a gaseous fuel receiving chamber for deliveryto an engine cylinder, means for compressing gaseous fuel in said fuelchamber, and a pressure regulated valve: receiving high pressure gaseousfuel from a reservoir of said fuel and connected to deliver to said fuelchamber, said valve having a movable tapered plug portion and a shaftportion, and having means defining a pair of compartments each dividedby the diaphragm of different sizes subjected on opposite sides to fuelchamber pressure and crankcase pressure respectively, said shaftconnected to said diaphragm for differentially controlling the travel ofthe movable plug portion of said regulator valve.

5. The method of operating an internal combustion two-cycle engine on agaseous fuel comprising metering gaseous fuel at a pressure which is afunction of the pressure in the engine crankcase and a function of thefuel source, and forcing the fuel at said metered pressure into thecombustion chamber on the compression stroke of the piston after thepiston has passed the intake and exhaust ports.

6. The method of operating a two-cycle internal combnstion engine on apressurized gaseous fuel in a container which comprises measuring thepressure of the fuel in the container and the pressure of the crankcase,metering a fixed volume of fuel to the combustion chamber for eachstroke of the engine at a pressure which is in inverse proportion to thepressure of the fuel in a container and in direct proportion to thecrankcase pressure of the engine.

7. In a gas burning piston engine having a cylinder and a pistonreciprocal therein, a crankcase pressurized by the piston, an enginedriven fuel injection device connected to deliver to the cylinder, and apressure responsive fuel metering device connected lto be controlled byengine crankcase pressure and connected to deliver to said injectiondevice.

8. In an internal combustion engine of the two-cycle type theimprovements which comprise a gas fuel injection system for said engineincluding a source of gas fuel under pressure, an engine driven fuelinjection device connected to deliver to a cylinder of the engine, and apressure responsive fuel metering device connected to be controlled bythe pressure of said pressure fuel source and connected to deliver fuelto said injection device.

References Cited in the file of this patent UNITED STATES PATENTS821,915 Altham May 29, 1906 1,271,942 Ricardo July 9, 1918 1,614,736Kjellberg Jan. 18, 1927 1,747,171 Hubbell Feb. 18, 1930 2,636,487 FowlerApr. 28, 1953 2,763,248 Green et al. Sept. 18, 1956 FOREIGN PATENTS276.805 Italy Aug. 18, 1930 1,129,020 France Sept. 3, 1956

